Solid state crystal display having two isolated end cell regions

ABSTRACT

A single crystal material, such as gadolinium molybdate, is electrically excited to modulate transmission of plane polarized light. The memory characteristics and the sharp threshold characteristics are relied on to produce selection switching of the domains. Domain injection techniques are utilized for reducing domain coupling characteristics.

' a fazw an 0 United State Q [H1 3,862,795

f Tellerman X51024 1 Jan. 28, 1975 [54] SOLID STATE CRYSTAL DISPLAYHAVING 3.374.473 3/!968 Cummins 350/150 TWO ISOLATED END CELL REGIONS3.53l.l82 9/l970 Land et al ISO/I50 3.559.125 l/l97l it 1-1 .350150 [75]lnventor: Jacob Tellerman. Baysidc. N.Y. OTHER :SLLZATIONS I 7 A z 3]Sslgnee git z z New Land. Ferroelectric Ceramlc Electrooptic Storage andDisplay Devices, Sandia Corp. Reprint ScR-6- [22] Filed: Sept. 3, 19707-l2l9. Oct. 1967. pp. l7-20. 42-44.

' 2l A l. N ,1 69,289

[ 1 pp 0 Primary Examiner-John K. Corbin Attorney. Agent, orFirm-Cynthia Berlow [52] U.S. Cl 350/150, 340/1732. 350/l57 [5 1] Int.Cl. G02 1/26 57 ABSTRACT [58] Field of Search 350/l50. I51, 320;

340/!73 LS A single crystal material, such as gadolinium molybdate, iselectrically excited to modulate transmission [56] References Cited ofplane polarized light. The memory characteristics and the sharpthreshold characteristics are relied on to UNITED STATES PATENTS produceselection switching of the domains. Domain 350/15) injection techniquesare utilized for reducing domain 2.928.317 3/1960 Haines 350/50 couplingcharacteristics.

3.027.806 4/1962 Koelsch 3.l64.8l6 l/l965 Chang et al 350/l5l 3.374.3583/1968 Majima 350/l50 13 Claims, 19 Drawing Figures PATENTEB JMIZBIWSsum 10? 5 22 2.6 PULSE AMPLITUDE- RATIO TO DC THRESHOLD VOLTAGE o 0 0 00 0 0 mozoummjfli z 1.5:: wm 5m mvsmon fic'ai fifmw 'y p ATTORNEY SOLIDSTATE CRYSTAL DISPLAY HAVING TWO ISOLATED END CELL REGIONS BACKGROUND OFTHE INVENTION Optical activity and birefringence has been observed inmany crystal materials, especially crystals that have piezoelectricactivity. The gadolinium molybdate crystal materials are of particularinterest because they exhibit the optical effect and memory. That is,when properly excited, the dipoles are switched into a new direction andremain there until re-excited to switch back to original position. Thedipole reversal introduces a change in mechanical strain and in opticaleffects. Domain is used herein'to designate a group of dipoles orientedin the same direction.

SUMMARY OF TI-IE INVENTION This invention relates to the use of a singlecrystal material (such as gadolinium molybdate) for modulating thetransmission of light by means of electrical excitation to achieve aninformation display panel. While the gadolinium molybdate crystal hasshown birefringence and effective changes in the birefringencecharacteristics, the present invention is concerned with a displaytechnique which utilizes the ability of the crystal to rotate planepolarized light 90 in response to electrical excitation. The memorycharacteristics of the crystal wherein its domains remain oriented inthe directions given by electric field polarization makes the crystaluniquely suited to display applications. The crystal providesparticularly desirable'effects because of another factor, namely, itsthreshold characteristics. The threshold characteristic for gadoliniummolybdate, for example, dictates that an electric field of at least 12volts per mil of thickness is required before domain switching canoccur. Thus, a change in the optical effect is created only by exceedingthe threshold field. It is necessary, however, to exceed the thresholdby only a small amount in order to cause all dipoles to switch in thedirection of the applied field to form a single domain.

In the illustrated display panel embodiments, a gadolinium molybdatecrystal controls the transmission of impinging light in selected regionsor cells which, after electrical activation, remain in the conditionthus determined.

The single crystal panel has its C-axis normal to the plane of the paneland plane polarized light is incident upon the panel at an angle withina few degrees of its C-axis. XY electrical matrix selection networks areprovided for selective control of the panel. The crystal material isarranged in a matrix array to reduce domain coupling sufficiently toallow individual control of adjacent crystal cells. A domain injectiontechnique is also utilized for reducing the inherent domain couplingcharacteristics of the material. In particular, domain injection isutilized to provide oppositely polarized domain traps at opposite endsof stick-type crystal elements. Other applications of stick crystals areshown to exhibit one-dimensional type scanning such as tliermometer orwindow shade effects.

Other features and advantages of the invention will be apparent from thefollowing description and claims and are illustrated in the accompanyingdrawings which show structure embodying preferred features of thepresent invention and the principles thereof, and what is now consideredto be the best mode in which to apply these principles.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings forming a partof the specification. and in which like numerals are employed todesignate like parts throughout the same:

FIG. 1 is a diagrammatic view illustrating a direct view type displaypanel arrangement in accordance with the present invention;

FIG. 2 is an enlarged fragmentary view showing a sandwich-typearrangement comprising a polarizer. a panel and an analyzer;

FIG. 3 is a diagrammatic view showing a projection screen type ofdisplay panel arrangement in accordance with the present invention;

FIG. 4 is a diagrammatic view showing the effective electrical matrixnetwork of the display panel;

FIG. 5 is an enlarged fragmentary perspective view of a display panelhaving a crystal matrix wherein individual crystal cells aremechanically isolated;

FIGS. 6 and 7 are fragmentary detailed sectional views taken asindicated on the lines 66 and 7-7, respectively on FIG. 5;

FIG. 8 illustrates a display panel having a crystal matrix utilizing acrystal stick array;

FIGS. 9 and 10 are fragmentary detailed sectional views taken asindicated by the lines 9-9 and 10-10 on FIG. 8;

FIG. 11 is a perspective diagrammatic illustration of a computer memoryapplication utilizing a display panel in accordance with this invention;

FIG. 12 is a fragmentary perspective view similar to FIG. 8 and showinganother embodiment of the invention wherein crystal sticks have domaintraps at opposite ends;

FIG. 13 is an enlarged fragmentary sectional view taken as indicated onthe line 13-13 of FIG. 12;

FIG. 14 is a view similar to FIG. 13 and showing an alternative stickarrangement;

FIG. 15 is a side view of a crystal stick and electrical energizingcircuit combination;

FIG. 16 is a graph showing the electrical field profile DETAILEDDESCRIPTION OF THE INVENTION Referring now to the drawings, andparticularly to FIG. 1, a diagrammatic illustration is given of adisplay panel embodiment for presenting black and white display ofinformation. The arrangement utilizes a flat planar panel 10 of a singlecrystal material having transparent electrodes 10E on opposite sides tobe voltage controllable by means of electrical field excitation formodulating the transmission of light through the panel.

In the illustrated embodiment, the panel is of gadolinium molybdatecrystal having its C axis or axis of symmetry oriented perpendicular tothe plane of the slab. Plane polarized light, as indicated at 11, isshown incident upon the panel at an angle of incidence aligned with orat least within a few degrees of the crystals C axis. The transmissionof such plane polarized light through the panel is modulated byapplication to the crystal material of an electric field oriented in thedirection of the C axis.

To provide plane polarized light, a light source 12 is shown at thefocus of a parabolic reflector 13 to create collimated light which,after passage through a polarizer 14, provides only plane polarizedlight incident upon the panel. An analyzer 15 is located on the oppositeface of the panel. For initial adjustment. the analyzer 15 is rotated toa position allowing maximum light transmission. The transmission oflight through the panel 10 is reduced by a large factor by exciting thecrystal material with an electrical field to switch it to a conditionopposite to that which existed for the initial setting. Substantiallycomplete extinction of light transmission can be approached in the caseof single crystal material such as gadolinium molybdate.

The effect of altering the electric field excitation appears to causethe plane of polarization of the incident light to be rotated 90 withrespect to the initial condition. The apparent range of the modulationeffect can be increased somewhat by utilizing monochromatic light as thesource 12. As is shown in FIG. 2, the single crystal panel 10, thepolarizer 14, and the analyzer 15, are mounted in sandwiched relationrather than being spaced apart as in the diagrammatic representation ofFIG. I.

The light emerging from the analyzer 15, being plane polarized, presentsa field of view spanning only a few degrees, so that a viewer would haveto be located substantially directly in line with the direction oftransmission. For practical information display systems, a diffuserplate 16 is shown intercepting the light projected from the analyzer 15to create a display having a field of view of approximately 180. Thediffuser plate 16, as shown herein, is an opal flashed glass platehaving a coating 16C of opal material upon its upstream face. Thediffuse surface can also be a ground or etched plate of glass.

As shown in FIG. 3, a modified embodiment for enlarging the illuminateddisplay includes a projection lens 17 located downstream of the analyzer15, with a light diffuser screen 18 being provided to receive the lightprojected from the lens 17.

In the preferred practice of the invention, the single crystal panel 10effectively constitutes a twodimensional matrix for which an electricalschematic is shown in FIG. 4. The matrix is controlled from any suitablesignal source which incorporates an X-Y coincident voltage addressingfunction analogous to the coincident current addressing techniqueutilized in magnetic core memory systems. Thus, the signal source hasprovisions for energizing any one of the horizontal row electrodes Y, toY; and has provisions for energizing any selected ones of the verticalro electrodes X to X These rows of electrodes, as explained hereinafter,are located on opposite faces of the panel and the crossing points ofthe energized electrodes define and control the individual crystalelements or cells which collectively constitute the matrix. As shown inFIG. 4, each crossing ofthe row and column electrodes on the oppositefaces of the crystal may be represented by an equivalent discretecapacitor. Thus. by exciting one of the column electrodes, for example.X and one of the row electrodes, for example, Y the excited crystalelement is element 20 shown in FIG. 4. The manner of excita-' tion is toapply a positive halfvoltage (+V/2) to the column electrode X and anegative half voltage (-V/Z) to the row electrode Y so that full voltage(V) is applied across the selected crystal element to effect the desiredoptical switching action of such element. By applying opposite voltagepolarities, the element 20 may be switched back to its initialcondition.

It should be noted that the signal selector source operates so that allof the electrodes which are not cnergized are connected to ground duringthe excitation of electrodes X and Y Thus, all of the remaining crystalelements controlled by the horizontal electrode Y and all of theelements controlled by the column electrode X have only a half voltage,or respectively, acting thereacross, and will not be switched from theirassumed initial condition. Once an element of the display is excited. itremains excited, without further or continued excitation because of theoptical memory characteristic of the crystal material that is utilized.In addition, any element of the display may be reset by reversing itsprevious state of electrical excitation so that full or partial erasurecan be provided as desired. I

While gadolinium molybdate is the currently preferred material for thepractice of the invention, other materials having comparablecharacteristics are contemplated within the scope of this invention. Inparticular, the characteristics which are of principal impor tance arethe ability of the crystal material to effect a rotation of the plane ofpolarization of the light incident upon the crystal, the optical memoryeffect which enables the crystal material to remain in its set state andto be switched from that state only by reverse polarization, and thesharp threshold characteristic. In the case of gadolinium molybdate, theelectric field should be 12 volts per mil of thickness or greater inorder to cause it to switch states of light transmission. The appliedvoltage is thus set to exceed the threshold value to a limited extent sothat the half voltage level remains well below the threshold. Thisenables selective switching of discrete regions of the matrix and itenables the entirety of each such discrete region to switchinstantaneously and uniformly.

In the case of gadolinium molybdate, the ratios of maximum lighttransmission to light transmission at cutoff are larger where thecrystal thickness is above 0.010 inches.

A number of mosaic or semi-mosaic structural arrangements are providedin the preferred practice of the invention. The crystal material can beshown to be comprised of groups of dipoles oriented in the samedirection, such a group of dipoles being referred to as a domain. If oneelement or cell of the matrix is switched, it is necessary that alldipoles therein undergo rotation in order to achieve the desired opticalchange for the element. The domain in one element, upon being switched,tends to produce a switching effect in neighboring unexcited regionswhere only a half strength electric field exists. Domains have a strongcoupling in one direction but a comparatively weak coupling in aperpendicular direction.

The matrix arrangement in FIG. 5 is comprised of a two-dimensional arrayof square crystal elements, each of which represents a separatelyswitchable element of the display. 'Ihcse individual squares areinterconnected into a composite matrix panel by means of a mechanicalgrid work of intersecting webs W of suitable filler material, such as anelastomer.

The raw electrodes 74,, X etc. are shown as including connection tabs 21leading from the edge cells X,Y,, X Y etc., bridging tabs 22 (FIG. 6)overlying the webs W and full surface conductive coatings 23 on thecorresponding cell surfaces and interconnected by the bridging tabs 22.

Similarly, the column electrodes Y,, Y etc., are shown as includingconnection tabs 24 leading from the edge cells X,Y,, X,Y etc., bridgingtabs 25 (FIG. 7) overlying the webs W and full surface conductivecoatings 26 on the corresponding cell surfaces and interconnected by thebridging tabs 25.

In this mosaic arrangement, the elastomer webbing W between the discretecrystal elements prevents mechanical coupling and stressing effects dueto the domain switching characteristic of the material. The mosaic ismanufactured by first growing a single crystal structure which is cutinto panels by slicing in a plane perpendicular to the C axis. Eachpanel is the approximate size of the final mosaic panel and is furtherprocessed by providing conductive coatings 23, 26 on its opposite faces.A thin vacuum deposited metallic film may be used with some sacrifice inlight transmission. Metallic oxides, such as stannons, cadmium or indiumoxides, provide less light attenuation.

The electroded panel is then slit into elemental squares or cells bycutting with a wire saw, first in one direction and then in anorthogonal direction, with the slots formed by the cutting being filledwith elastomer material which is cured in situ.

Finally, the bridging electrode tabs 22, 25 are vacuum deposited uponthe webs to complete the desired grid work of electrode connections.

Another mosaic panel arrangement is shown in FIGS. 8,9 and 10. Itemploys a glass substrate 27 having crystal strips or sticks 28 inclosely spaced side-by-side relation. Opposite faces of the panel fromwhich the sticks 28 are cut are coated as previously indicated so thatthe underface of each stick is provided with a transparent electrode 29extending along its full length. Each stick is effectively subdivided byproviding a set of grooves 28G in spaced relation along the uppersurface to provide mechanical discontinuities which minimize the domaincoupling effect between neighboring cells of the are shown connected tothe underface electrode coatings 29. Column electrode tabs 33 are shownconnected to the upper face electrode coatings 30.

The arrangement of FIG. I as already indicated is particularly useful inan information display system wherein the light transmissioncharacteristic of the crystal material is selectively controlled by thestrength and polarity of the electrical field excitation so that a trueblack and white visible indication is produced for viewing.

The same basic panel structure, such as is shown in FIGS. 5 and 8, isuseful in other information systems such as a computer memoryarrangement wherein the information to be stored is in the form ofabinary code. In a computer memory application as shown in FIG. I I, thestorage matrix 35 is selectively excited and the pattern of domainpolarization which is thus established will remain after the excitationis removed. For readout, the matrix 35 is shown associated with a singleoutput photocell 36 and with a flying spot scanner 37 which generates aline-by-Iine raster pattern so that the individual data bits are readout in sequence.

A further panel embodiment is shown in FIG. 12

'where a matrix arrangement is comprised of a set of crystal sticks 38which are arranged in parallel relation upon a glass substrate andspaced apart by webs W. In this form, each stick is provided with aseparate groove 38G adjacent each end and serving to define end cells38A,38B which function as domain traps in the final matrix. Scribe linesare shown in phantom as indicated at 388 to define the intermediate cellregions of each stick. The scribe lines 388, as shown in the enlargedfragmentary view of FIG. 13, represent discontinuities in the surfaceelectrode coatings 39 and may be formed by discrete electrode coatingsas initially applied or by etching of full surfaced coatings or by sawcuts (that is, similar to the grooves 280 of FIGS. 8 and 9).

Each of the sticks 38, as described more completely hereinafter, issubdivided into a set of intermediate cells which are part of theelectrical matrix and end cells or domain traps 38A, 383 which are notpart of the electrical matrix. The domain traps of each stick areoppositely polarized electrically by means of a domain injection processdescribed hereinafter and remain unchanged during use of the matrix. Theintermediate cells are of random polarization and are capable ofindividual polarization in accordance with the applied matrix voltages.The provision of the domain traps 38A,38B at opposite ends of the sticks38 allows the independent switching of the domains in the intermediatecells. It is believed that since the domain traps prevent the domainsfrom aligning along the entire length of the stick, as is the normaltendency due to the domain coupling relationshipof such crystalmaterials, the domain coupling is essentially disrupted thereby allowingthe intermediate cells to be independently oriented in accordance withthe applied electric fields.

It may be noted that the grooves 28G between adjacent cells in theembodiment of FIGS. 8 and 9 are provided for reducing domain couplingbetween adjacent cells. As shown in FIG. 14, a stick 39 may be providedwith domain traps 39A,39B and with isolation grooves 39G for use in amatrix arrangement as shown in FIG. 12.

DOMAIN INJECTION The domain trap configuration as previously referred toconsists in providing domain traps of opposite orientation at oppositeends of the stick. The stick is provided with grooves to delineate thetrap regions and as indicated previously the intermediate region of thestick may be smooth or may be provided with grooves to delineate theindividual cells. With either stick configuration, the process of domaininjection is the same and consists of:

l. Bringing the stick up to Curie temperature, ap-

proximately l60C, so that the domains assume a random pattern oforientation;

2. Applying opposite voltage bias to successive intermediate cells;

3. Applying positive voltage to one end region and negative voltage tothe other end region;

4. Slowly bring the temperature of the stick down from Curie temperatureto provide domain traps of opposite orientation at extreme ends, thesedomains being oriented perpendicular to the long axis.

The domain trap principle is utilized in gadolinium molybdate stickarrangement for providing other optical display effects. For example, inFIG. a stick 40 is shown with grooves 406 to define domain traps 40A,40Bwhich are oppositely polarized as previously described to reduce thedomain coupling and allow the intermediate stick regions to beselectively polarized.

The stick 40 has an underface coating 41 of any suitable transparentconductive material and has an upper face coating 42 of a high resistivematerial, such as indium oxide, which spans the stick regionintermediate the grooves 400. Domain traps 40A,40B of opposite polarityare defined at the ends of the stick 40. Typically, the resistance ofthe indium oxide coating from terminal to terminal is 200 K ohms.

The stick is arranged for connection in circuit with a source S ofvariable DC voltage and, as shown, includes a connection terminal 43 atone extreme end which is to be connected to the positive polarityterminal of the source and a connection terminal 44 at the opposite endof the indium oxide coating which is connected to ground through avoltage dropping resistor 45. The under face coating 41 is connecteddirectly to ground. The indium oxide coating 42 electrically is inseries with the resistor 45 to function as a voltage dropping networkwhich determines the voltage gradient profile across the stick.

The profile chart of FIG. 16 shows a pair of voltage gradient profilelines A,B to illustrate the control of domain switching that can beachieved by the combination illustrated in FIG. 15. For example, voltageprofile line A which is for a relatively low applied voltage indicatesthat the voltage gradient across the stick is a maximum at the left endof the indium oxide coating and is a minimum at the right end. A typicalvoltage gradient threshold line T, for example for a gadoliniummolybdate crystal stick, is shown in the graph. Domain switching occursat regions of the stick where the voltage gradient exceeds the thresholdlevel T.

Thus, application of a DC voltage corresponding to the profile line Awill cause the entire region of the stick between the left hand terminaland the intersection point P to switch domains because the fieldstrength at such region exceeds the threshold field strength T. Theportions of the stick to the right of the point P will not switchdomains. The resultant optical effect in a system such as shown in FIG.1 is a bar type indication in the nature of a thermometer or windowshade action.

If the applied voltage is increased to a higher level to determine avoltage profile line B, the entire region of the stick intermediate ofthe grooves 400 will switch domains. Therefore, the length of the stickregion which switches domains is a function of the level of the appliedvoltage. The optical contrast ratio between the I fashion to stop shortof the end of the opaque region. v

switched regions and the remainder is about 10 to 20 to one.

An alternative stick 50, as shown in FIG. 17, is of uni-' form taperfrom end to end and is provided with grooves 506 to define domain traps50A,50B of opposite orientation. The stick 50 has a trnsparentconductive coating 51 on its underface and a transparent conductivecoating 52 spanning the region of its upper face intermediate thegrooves 500. DC voltage from a variable voltage source S is applieddirectly across the coatings 51,52 to produce a voltage gradient varyinglinearly along the length of the stick. the gradient being greatest atthe narrow end and lowest at the thick end. The point at which thegradient exceeds the threshold value determines the region of the stickwhich will undergo domain switching. The length of the region thatswitches is directly proportional to the level of the applied voltage sothat the stick arrangement of FIG. 17 provides a thermometer or windowshade effect analogous to that of the stick of FIG. 15.

Another stick arrangement for producing this same effect is shown inFIG. 18. In this form, the stick 60 is tapered in the direction of itswidth and is provided with electrode coatings 61,62 in the fashion ofthe stick of FIG. 17 such that DC voltage applied from a source Sproduces a field which is uniform along the length of the stick. Thestick 60 is shown with grooves 60G that define oppositely orienteddomain traps 60A,60B.

The domains near the wide end of the stick are easiest to switch whilethe domains closer to the crowded or converging end of the stick presentincreasing resistance to domain switching. An applied voltage from thesource S produces domain switching beginning at the left end andprogressing lengthwise to a point determined by the value of the appliedvoltage. If the applied voltage is increased the region of domainswitching elongates.

Any of the stick configurations of FIGS. l5, l7 and 18 can be controlledin accordance with a further property exhibited by the crystal material,namely, the property wherein domain switching begins at one end andpropagates lengthwise at a predetermined rate. Accordingly, theinvention contemplates the use of a gated source S that is adjustablefor applying voltage pulses of variable time duration selected toterminate the domain propagation. Typically, the time constant of domainpropagation for gadolinium molybdate is about 20 milliseconds per inch,though there is a time delay associated with initiation of the domainswitching. After the initial time delay, the propagation itself israpid. The chart of FIG. 19 provides a response time curve taken forgadolinium molybdate crystals threeeighths inches in diameter and 0.15to 0.20 inches thick.

Additional optical display characteristics can be provided with thedomain trap-type stick arrangements. For example, a stick may be domainswitched in a fashion to propagate black" from left to right to producea continuous opaque region of predetermined length. The stick is thenexcited with DC voltage of opposite polarity to propagate white" fromleft to right in a The length of each propagation may be controlled as afunction of voltage level or time, as previously indicated. An opaquemark will remain of a width determined by the amount of the blackpropagation that is not erased by the subsequent white propagation.

In any of the embodiments disclosed herein, the matrix cells may beformed with discrete coatings, for example, a separate coating for eachcell quadrant so that the X-Y address system is subdivided by a factorof 4. Each cell is in effect four subcells. A relatively small compositegrouping, such as 4, makes it possible to domain switch each sub-regionindividually even though the cell is not subdivided mechanically. Thisallows development of gray tones by reason of the higher resolution thatis made possible. The gray tone effect is more easily achieved in cellstructures of sticks having domain traps as described herein.

A further concept for producing gray tones is based on the use ofpartial switching. in this approach. any selected cell is excited by avery narrow pulse timed to effect switching ofonly part of a cell. Thus,the fraction of the cell that switches is determined by the duration ofthe pulse to permit the effect of gray shade to be generated.

Thus, while preferred constructional features of the invention areembodied in the structure illustrated herein, it is to be understoodthat changes and variations may be made by those skilled in the artwithout departing from the spirit and scope of the appended claims.

What is claimed is:

l. A system for electronic control of optical transmission comprisingpanel means having an axis of symmetry perpendicular thereto, said panelmeans comprising a mosaic of parallel spaced apart gadolinium molybdatecrystal sticks arranged in side by side relation to providea matrixarray of individually controllable crystal cells, each stick includingan equal number of intermediate crystal cells collectively constitutingsaid cells of said matrix and two isolated end cell regions, electricalmeans controlling selective energization of any of said matrix cells,optical means for directing plane polarized light upon said panel meansat an angle of incidence within a few degrees of said axis, saidelectrical means effecting selective electric field excitation of thematrix crystal cells in the direction of said axis for producing domainswitching activity within each selected crystal cell for rotating planepolarized light to effect modulation of the light transmissioncharacteristics thereof, and said isolated end cell regions of eachstick being of predetermined, fixed and opposite polarization forlimiting domain coupling effects between said cells of said matrix.

2. A system for electronic control of optical transmission as defined inclaim 1 wherein said electrical means includes row electrode means andcolumn electrode means overlying opposite faces of the panel means.

3. A system as defined in claim 1 wherein said optical means includes asource of collimated light, a polarizer between said source and saidpanel means and an analyzer on the opposite side of said panel.

4. A system as defined in claim 1 and including a display screenintercepting light transmitted through said panel means, said screenhaving a diffusion surface to provide a display characterized by a wideangle field of view.

5. A single crystal element responsive to electric field actuation toeffect control of optical transmission, said element comprising a stickof crystal material exhibiting a bistable optical memory characteristicand further exhibiting domain switching activity at a sharply definedthreshold level capable of rotating plane polarized light, said stickhaving two isolated end cell regions of predetermined, fixed andopposite polarization for limiting domain coupling effects at thenon-isolated intermediate regions thereof and electrode means connectedto opposite intermediate face regions of the stick to control selectiveelectrical field excitation thereof.

6. A single crystal element as defined in claim 5 and wherein said stickhas transverse surface grooves in one of said faces defining andisolating said end cell regions.

7. A single crystal element as defined in claim 5 wherein said stick hastransverse surface grooves in one of said faces defining and isolatingsaid end cell regions, one of said electrode means includes atransparent conductive coating overlying substantially the entireintermediate region of one of said faces and the other ofsaid electrodemeans includes a transparent high resistance coating overlyingsubstantially the entire intermediate region of the other of said faces.

8. A single crystal element as defined in claim 5 wherein said stick hastransverse surface grooves in one of said faces defining and isolatingsaid end cell regions, said stick being tapered in thickness toprogressively vary the spacing of said faces.

9. A single crystal element as defined in claim 5 wherein said stick hastransverse surface grooves in one of said faces defining and isolatingthe end cell regions, said stick being tapered in width to provideuniformly spaced faces of tapering width.

10. A single crystal element as defined in claim 5- wherein said crystalmaterial is gadolinium molybdate;

11. A system for electronic control of optical transmission comprising astick of single crystal gadolinium molybdate exhibiting a sharp electricfield threshold of domain switching activity capable of rotating planepolarized light, said stick having two isolated end cell regions ofpredetermined, fixed and opposite polarization for limiting domaincoupling at the non-isolated intermediate regions thereof, andelectrical source means including electrode means connected to oppositeintermediate face regions of the stick for applying an electric fieldadjacent one extreme of the intermediate face regions to propagatedomain switching activity a controlled distance lengthwise along thestick.

12. A method of manufacturing a stick of single crystal materialthatexhibits selective domain switching activity capable of rotating planepolarized light in response to selective electric field actuation, saidmethod including providing end cell regions of opposite orientation atopposite ends of the stick by bringing the stick material up to Curietemperature to allow the domains to assume random orientation, applyingopposite voltage bias to successive intermediate cells, applyingpositive voltage at one end and negative voltage to the other end of thestick and maintaining the applied voltage relationships while bringingthe temperature of the stick down from Curie temperature to provide endcell regions at the ends of the stick oriented perpendicular to the longaxis of the stick.

13. A method as defined in claim 12 and including the step of formingsurface grooves to border and define the end cell regions.

1. A system for electronic control of optical transmission comprisingpanel means having an axis of symmetry perpendicular thereto, said panelmeans comprising a mosaic of parallel spaced apart gadolinium molybdatecrystal sticks arranged in side by side relation to provide a matrixarray of individually controllable crystal cells, each stick includingan equal number of intermediate crystal cells collectively constitutingsaid cells of said matrix and two isolated end cell regions, electricalmeans controlling selective energization of any of said matrix cells,optical means for directing plane polarized light upon said panel meansat an angle of incidence within a few degrees of said axis, saidelectrical means effecting selective electric field excitation of thematrix crystal cells in the direction of said axis for producing domainswitching activity within each selected crystal cell for rotating planepolarized light to effect modulation of the light transmissioncharacteristics thereof, and said isolated end cell regions of eachstick being of predetermined, fixed and opposite polarization forlimiting domain coupling effects between said cells of said matrix.
 2. Asystem for electronic control of optical transmission as defined inclaim 1 wherein said electrical means includes row electrode means andcolumn electrode means overlying opposite faces of the panel means.
 3. Asystem as defined in claim 1 wherein said optical means includes asource of collimated light, a polarizer between said source and saidpanel means and an analyzer on the opposite side of said panel.
 4. Asystem as defined in claim 1 and including a display screen interceptinglight transmitted through said panel means, said screen having adiffusion surface to provide a display characterized by a wide anglefield of view.
 5. A single crystal element responsive to electric fieldactuation to effect control of opTical transmission, said elementcomprising a stick of crystal material exhibiting a bistable opticalmemory characteristic and further exhibiting domain switching activityat a sharply defined threshold level capable of rotating plane polarizedlight, said stick having two isolated end cell regions of predetermined,fixed and opposite polarization for limiting domain coupling effects atthe nonisolated intermediate regions thereof and electrode meansconnected to opposite intermediate face regions of the stick to controlselective electrical field excitation thereof.
 6. A single crystalelement as defined in claim 5 and wherein said stick has transversesurface grooves in one of said faces defining and isolating said endcell regions.
 7. A single crystal element as defined in claim 5 whereinsaid stick has transverse surface grooves in one of said faces definingand isolating said end cell regions, one of said electrode meansincludes a transparent conductive coating overlying substantially theentire intermediate region of one of said faces and the other of saidelectrode means includes a transparent high resistance coating overlyingsubstantially the entire intermediate region of the other of said faces.8. A single crystal element as defined in claim 5 wherein said stick hastransverse surface grooves in one of said faces defining and isolatingsaid end cell regions, said stick being tapered in thickness toprogressively vary the spacing of said faces.
 9. A single crystalelement as defined in claim 5 wherein said stick has transverse surfacegrooves in one of said faces defining and isolating the end cellregions, said stick being tapered in width to provide uniformly spacedfaces of tapering width.
 10. A single crystal element as defined inclaim 5 wherein said crystal material is gadolinium molybdate.
 11. Asystem for electronic control of optical transmission comprising a stickof single crystal gadolinium molybdate exhibiting a sharp electric fieldthreshold of domain switching activity capable of rotating planepolarized light, said stick having two isolated end cell regions ofpredetermined, fixed and opposite polarization for limiting domaincoupling at the non-isolated intermediate regions thereof, andelectrical source means including electrode means connected to oppositeintermediate face regions of the stick for applying an electric fieldadjacent one extreme of the intermediate face regions to propagatedomain switching activity a controlled distance lengthwise along thestick.
 12. A method of manufacturing a stick of single crystal materialthat exhibits selective domain switching activity capable of rotatingplane polarized light in response to selective electric field actuation,said method including providing end cell regions of opposite orientationat opposite ends of the stick by bringing the stick material up to Curietemperature to allow the domains to assume random orientation, applyingopposite voltage bias to successive intermediate cells, applyingpositive voltage at one end and negative voltage to the other end of thestick and maintaining the applied voltage relationships while bringingthe temperature of the stick down from Curie temperature to provide endcell regions at the ends of the stick oriented perpendicular to the longaxis of the stick.
 13. A method as defined in claim 12 and including thestep of forming surface grooves to border and define the end cellregions.